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Triumph TR6 - braking problems

I have 2 braking problems with my TR and have had this problem for a couple of years. First off the braking system has rebuilt Calipers (new pistons and seals) new rotors and pads, new rear cylinders, rebuilt master and new flex lines all around, no leaking in the system, and DOT 4 Lockheed fluid.

1.under normal braking circumstances the pedal is firm and hard (no puns intended) and get terrific braking power. However after backing up and turning out of my driveway (still in reverse) the next time I apply the brakes the pedal travels about half way down. After this initial sink, subsequent braking actions are normal and feels fine. This sometimes also occurs only when I am hard turning ie steering fully cranked over when negotiating a parking spot. Other than this inital problem I never have to 'pump the pedal' to get pressure so I assume that I am not getting any internal leaking in the master. It only seems when the car is turned hard over durring low speed maneuvers.

2. Durring dry braking circumstances the car stops very effeciently and quickly, if fact it seems more powerful and quicker than my modern car Acura CL. Problem is when it is raining or on wet roads, if I have to do a panic stop or aggressive braking action the fronts lock up and slide. The car still tracks straight durring this but now braking distance is unreal and to the point of being scarry as I don't want to smack up the front by plowing into the car ahead of me. My tires are newish (4yrs) Yokohamas 205/7015 and wondering if the oversize (wider) comprimises wet braking conditions as the surface area is wider and being a light car the weight is not concentrated to the ground. My theory is similar to snow tires where narrower is better and with race cars having difficulty braking in the wet even with rain tires.
Steven

Steve,

I don't have your first problem. But, I too find it really easy to lock up the front end on hard braking.

With two aomewhat heavy people and coming down from say 50mph into a tight right or left hander, I lock up unless I am extremely careful.

I hasten to add that this is on dry tarmac with good tyres all round. Do I suspect lack of rear bracking, or possible crossed brake pipes at the master cylinder ?

Early braking seems the only solution, kind of silly really in a sports car though.

Any clues folks ?

Best Regards

Bob
Bob Blewitt

Steven,
Just an idea.
Does this happen any time you have to back, or only the first time you drive out? Is it an effect of leading shoe brakes? Perhaps in reverse the shoes are allowed to retracta a little further than normal, and there is more spacve in the system, until you pump it up, and the shoes work normally? Are all the shoe retaining springs etc present? Have you tried re-setting the brake shoe adjusters?
John
JohnD

Stephen,
It maybe a long shot, but if your problem occurs when you brake repeatedly during a short time, you might look at the vacuum hose being kinked. I had this problem, and read a posting somewhere about it, and it goes like this:

When you brake, the booster uses the vacuum and needs to be restored. If the hose is kinked, it takes a little while to restore the vacuum in the booster, where that should really occur immediately. This is apparently a problem because the cars were designed for right-hand drive where the hose connection would be relatively straighter and short.

So, if the time period between brakings appears to be a factor in your situation, you might want to look at the hose where it comes out of the intake manifold, to see if its kinked. I put a platice elbow to relieve the strain, and it cured the problems completely.
Good luck,
Mark
Mark H

Steven - For #1, are your front rotors thin, ie have they been turned down to the lower limit on thickness or even lower ? Some TR racers reported the same problem you ask about and they found out the caliper pistons worked fine in a straight line, but when they turned fast and hard, the calipers were being "sent back" into the caliper bodies and at the next hard braking point, the calipers came out but still didn't touch the rotor. Scarry !!!

I wonder if loose front wheel bearings cause this too ?

Don Elliott, 1958 TR3A
Don Elliott

Thanks for the suggestions, to answer some of the questions posed:

Front rotors are about 4 years old with 9,000miles, They are Brembo make and never been turned so thinness is not an issue, also they have newish pads AP Lockheed so therefore there is substantial thickness and the piston is far from coming out. Front bearings have been torqued to the correct ft/lbs and as listed in the manual...backed off 1 flat.

I had this problem prior to the caliper and master rebuild, and new rotor and pads.

Vacuum is straight with no kinks.

This problem only occurs when hard turning ie wheel at full lock either forwards or backwards. Under normal driving circumstances it is never an issue even when doing a 90* turn on to the next street at a stop light.

There is no crossed pipes at the master and I believe that they have different threads anyways.

Possible other issue could be a twisted flex line when the wheel is turned but I checked and it appears in-line.
Steven

Steve,
The first problem you describe ( the long pedal movement after reversing with steering lock ) is caused by play in the front wheel bearing(s). The steering lock puts sideways forces on the bearing and as the brake disc (rotor) rocks with the hub it pushes against the pads and drives the cylinders into the caliper- hence the intial long pedal motion. It's called 'knock-back' over here. Check for bearing play by pulling on the top of the tyre- you can feel the lost motion. Remove the wheel and the grease cap and then the split pin. Nip up the bearing to the recommended torque, fit a new split pin etc.
You'll soon get familiar with the job- those bearings are not really up to the job, and it's worth keeping a set to hand.
Peter Cobbold

Whatever the causes of our cars locking front wheels under heavy braking ( soft springs, worn shockers, narrow section tyres etc etc) there is remedy that costs nothing. But it needs a little practise.'Cadence breaking' involves banging your foot on and off the brake pedal as hard and fast as you can as soon as you feel the the front wheels lock up. It's the human form of ABS. It's counterintuitive to release the brakes but it really does work. Try it when no-one is following you on a straight road. The suspension will bang and crash under this abuse so I don't recommend it as a routine way to slow down, but in an emergency it really does work.
Peter Cobbold

Peter

To your suggestion of replacing the front bearings, any trick to removing that pain in the ass grease cap? It is perhaps the worst design ever and nothing grips that cap except brute force and that leaves the cap worthless and destroyed.

While I understand cadence braking, it seems to lock up the instant the ground is wet.
Steven

Steven
You might try some very large slip joint pliers to remove the (I agree) grease caps. Kinda wiggle them off. If no joy then full force and destroy...then buy new.. I welded a small nut on the inside of the cup then with a bolt I just turn the bolt in till it hits the face of the stub axle keep turning and the cup pops off. Oh ya... a little anti-sieze on the cup edge helps.
Regards
Rick C
Rick Crawford

Steven- Maybe The rotors and pads are to strong for the rear braking. There is an interesting web page I read about how to build an ajustable brake balancer with using parts from a mini.
Don K.
DON KELLY

Hi Steven

Sorry to have missed you at Bronte. We will all work on that one next year.

Next is theory only guys. Been off the Brit for awhile so please correct.

1: If your master reservour is as cloudy as mine. Make absolutely sure your back brake res. the front one is full. That little spillway can trick. I screwed up on this due to an angled driveway many years ago. Nothing you hate to hear more than the correct observation by your better half.

2: The backup turn thing I am going with JohnD. And DonE.

Front End
Did this problem start when you first put the wide tires on and are you using original wheels or offsets? Steel calipers will flex considerably under the right conditions. If your centering is off may kick just enough to create problem. Make sure Calipers are centered and true eyeball. Young Garage mechs. may not even think of that. Doesn't take much even with reg. tire/wheel. Calipers now float rather than using centering shims as the Tr does just for that reason. One possibility.

Rear End
Make sure emerg. brake is off and not too tight or binding.

Tighten up both rear wheels to can't turn by the brake adjusters with emerg. known off. Then back off only to scuff noise as you turn. This should take out most mechanical play. If your real energetic pull the wheels and bang out brake and rust dust first. The stuff on your front wheels stays in drum. If auto adjusters are froze the problem will return after a short time. We park the baby more than we drive and they rust. Never-Seeze and brake lube along with dialectric on the shelf in shop always.

3: Lockup hard braking.

If the British engineer designing the TR knew as much about front wheel lockup as any young fellow with a mountain bike we would not be having this discussion. Grab front brake at speed land on nose-tailbone-nose etc.

The master cylinder in TR is designed to engage the front discs first. The thinking I guess was disks are much more efficient get them online first. When you step on the brake your foot activates the front disk plunger then through a spring that plunger operates the rear brake plunger. Yep you have mostly front brake action unless your rears are at optimum. Not an engineer but thats what I see by manuals. And if that spring is a poor repop or 30 years old good luck. I don't know if the springs are currently included in a master rebuild kit?

People have been using brake biasing in racing and rodding for years you can buy fully adjustable valves depending on your front to rear weight ratio and needs to bring brake action into anywere you want it. May work on TR. not sure of the spring action business and I have never tried. At present we don't want Mom doing a slightly uncontrolled drift into the supermarket Although it will definatley bring her KOOL rating up with teenager.

Acura CL has ABS this, traction that traction etc. etc. car thinks for you. Probably impossible to put into a contolled drift or anything else. Work great for commuting I guess. Have a buick T-type from new 14 years and have disabled all ABS. Great when new and though well maintained stresses on car and wiring make them questionable. I do not trust any mechanical device thinking for me. You don't want to hear my view on air bags.

Back to cars. BOB and Steven.

Bob if all of the above is perfect. You should have a very very slight front biasing. Rear of the car pushing on hard cornering to let you get on it to contol slide. From what I can see that is the way it was designed. Colin Chapman or racing thinking. Any more check for warped rotor,caliper not centered back brakes way off. Want to hear back about that spring in master. A much younger fellow I know years ago enjoyed scaring the hell out of Corvette friends on tight turns. Never had a problem with front lock up. I heard he may still put V8 in TR and go looking for C5s. TOO OLD TO SOON. BUT IMMATURITY IS FOREVER.

Steven your Yokahamas should be fine in rain unless specificaly rated. You will never get Acura panic braking on wet roads though. Front brakes locked up will plane with any tire and back not doing much seems to be the case. Although you must be getting reasonable backs. In my experience you would be trying to swap ends. This keeps leading back to that Master Cylinder spring actuating back brake system or too much travel in back brake mech. Steven do you know if the spring was replaced or original in rebuilt. Could be a potential problem for everybody.

Good Luck
Bill







B Brayford

Steve,
Further to Rick's reply to your plea on removing the hubcap. To get the cap off in the first place, before you weld a nut inside, use a large selftapping screw through the hole in the cap top. This will only work once or twice, as the hole quickly becomes a larger hole.
Good luck!
John
JohnD

Stephen,
Re brakes locking up - I had a problem with general poor brake performance together with the front locking up under hard and not so hard braking and it was cured by properly adjusting the rear brake drums (if you have not done so allready) - as the rears are not self adjusting we have to force them to do their share of the work! Re Dust cover: I use a mallet and a sturdy flat blade screw driver applied to the side of the cover on an angle while working around the hub to remove the cover.
Mike

I would agree that the wheel bearings being too loose are the cause of this problem. Also, as far as the spindle cap..... there is a tool to properly remove these, I have owned one for many years. Just flag down your MAC or SnapOn tool man and buy one, they are not expensive. They are just simple large pliars with cross facing jaws that grip the cover jst past the lip. Steve Yott
Steve Y

This thread was discussed between 16/09/2002 and 18/09/2002

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